Method and means for reproducing optical images at a distance



March 8, 1938. E. D. PHINNEY 2,110,172

METHOD AND MEANS FOR REPRODUCING OPTICAL IMAGES AT A DISTANCE Filed Feb. 29, 1923 IN V EN TOR.

Patented Mar. 8, 1938 METHOD AND MEANS FOR REPRODUCING. OPTICAL IMAGES AT A DISTANCE Edward D. Phinney, Mount Vernon, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 29, 1928, Serial No. 257,891

18 Claims.

This invention relates to communication systems and in particular to those systems wherein messages are transmitted to a distance by means of optical images.

Various systems of transmitting optical images have heretofore been devised, for example, one type of system employs at the receiving station an image reproducer comprising a plurality of luminous points each corresponding to a definite area of the image to be transmitted. A system of this type is disclosed in United States Patent #1,595,'735.

Another type of system employs a single luminous spot of fixed area which is traversed by an analyzing element such as a spirally perforated disc. In all prior systems these receiving or image integrating devices have been open to the serious objection that they are necessarily dependent on the retentivity period of the human eye. That is to say, the original image was required to be analyzed into a certain minimum of points which were synchronously reproduced in succession on the receiving mechanism. Obviously therefore, the brilliancy of the image that could be reproduced was seriously limited by the number of points that could be projected in a unit time. That is to say, considering that the entire picture must be reproduced within at least onetwelfth of a second and assuming that the image is divided into 2500 luminous points, each luminous point at the receiving end is maintained brilliant for approximately only one thirtythousandth of a second. While the overall brilliancy of the picture mightbe increased by speeding up the number of total integrations per second this speeding up is seriously limited by the practical velocities attainable, and the consequent synchronizing problems encountered, with theuse of rotating commutators.

Accordingly it is one of the outstanding objects of the present invention to enable an image to be reproduced in discrete points wherein the over- .all brilliancy is greater-than can be attained with any apparatus according to the prior art. The above noted objectis attained by storing the successively transmitted impulses corresponding to each complete image on a suitable storing device and then using this stored record to reproduce the image visually as a whole. Consequently the entire image may be maintained on the visual reproducing means for a greater length of time than has heretofore been found possible.

It is a feature of the invention to provide a system for transmitting and'reprodu'cing optical images wherein the image is analyzed at the transmitting station in a point-by-point manner and is reproduced at the receiving station as a whole without regard to the point-oy-point analyzation.

Another/feature of the invention pertains to a imethodoflreceiving and reproducing image impulses whereby one completeimage may be visually reproduced simultaneously with the recording of another successive image.

Another feature pertains to the means for storing electrical image impulses prior to their visual reproduction.

A still further feature pertains to a novel image reproducing mechanism comprising a bank of lamps and improved commutator mechanism for controlling the integration of an entire image on 7 said bank of lamps.

Other features and advantages will be apparent after a consideration of the following description and the appended claims.

For the purpose of enabling a clear understanding to be attained of one manner of practicing the invention the same will be disclosed in connection with a television system of the general type shown in the United States patent to Schmierer Accordingly, Fig. l of the drawing shows schematically one well known form of image analyzing and transmitting mechanism.

Fig. 2 shows a receiving and image-integrating mechanism according to the invention.

Referring particularly to Fig. 1, the numeral I represents the object whose successive instantaneous images are to be transmitted, for example, one of the frames of a motion picture film. The picture or object is illuminated by any suitable light source represented by the numeral 2. The light which is reflected from the object I is collected by a suitable optical system represented by the numeral 3 and an image thereof is formed upon the analying disc 4 which may be of any type well known in the art pertaining to television. While it is preferable to employ a spirally perforated scanning disc for analyzing the image in a point by point fashion it will be understood that any other type of scanning mechanism may be employed. The light which passes from each successively scanned point of the image is collected by an optical system represented by the numeral 5 and is focused upon a light sensitive element 6 which is preferably in the form of a photo-electric cell of the potassium or potassium alloy type well known' to the art. The cell 6 therefore produces current impulses whose strengths are proportional to the light intensities of the successive image points.

Suitable amplifying mechanism represented schematically by the. numeral 1 amplifies the image currents before they are impressed upon the transmission line 8. If desired, instead of applying the image currents directly to-the line 8, these currents may be caused to produce a modulated carrier wave as is well known in the art of voice transmission. At the receiving station (Fig. 2) the image currents are preferably demodulated and yfurther amplified by suitable mechanism represented schematically by the numeral 9. I v

In systems according, to the prior art these amplified image current impulses have been transmitted directly and in succession to visual reproducing means which, for most practical purposes may take the form of a glow discharge lamp. Lamps of this character suitable for responding to image currents are wellknown in the art and further description thereof is notbelieved necessary. However, it is' preferable to' employ a glow discharge lamp of the general type disclosed in the United States Patentito Schmierer #1,595,'735, referred to hereinabove. As represented schematically in Fig. 2, this lamp comprises preferably a single large evacuated envelope a portion of which is represented by the numeral I0. Suitably mounted within the envelope are a series of strip-like metallic electrodes 'I I, I2, etc. Mounted within the envelope and in cooperative relation with each of the striplike electrodes II, I2, etc. are corresponding sets of separate small electrodes 13,14, I5, etc It is obvious therefore that each strip electrode, for example, the electrode I I, is common to the associated sets of separate electrodes I3, I4, etc; All the strip electrodes-may be connected together by a conductor I6 through one or more sets of electrical elementsII, to the-terminals ofa band of condensers C1. In this connection it may be noted that the capacities of the storing condensers and the elements are so chosen that for a given applied voltage the discharge currents through the lamp I0 produce the optimum optical effect as regards apparent brilliancyand permanency of impression. While. only two strip electrodes and cooperatingspaced-sets .of electrodes are shown in the -drawing,-it will be understood that a 'mu'ch'greater number will be employed. It will be obvious to those familiar with the art that the number of electrodes required will be determined by the degree of detail required in the reproduced image; For example, assuming that the original image produced by lens 3 is oneinch square, in-order that pleasing results .may be obtainedin the reproduction, it may be necessary to analyze this image into a plurality of successive points of the order of 2,000 and upward. Assuming that a 2,500 point analysis will give the requisite detail, the lamp ID will therefore be provided Witha set of '50 strip-like electrodes II,v l2, etc. eachgstrip electrode having associated therewith fiftyseparate electrodes I3, I4, I5, etc. This arrangement therefore provides a structure in which the. glow discharge elements are arranged in a coordinate relation so that a y point in the lamp may be illuminated simply by energizing the proper strip electrode and the desired one of the cooperating spaced electrodes. In Patent #l,595,'735 referred to hereinabove, there is disclosed mechanism-for producing a selective discharge between the desired sets of electrodes within the lamp, employing sets of cominutators which are rotated in synchronism with the analyzing mechanism at the sending end. y this arrangement the successive point-bypoint analysis at the transmitting end is trans.- lated into a corresponding ivoint-by-point illumination of the receiving lamp. 'With systems of this character it is obvious therefore that if a 2,500 point picture is to be reproduced in at least one-twelfth of asiecond; (corresponding to the minimum retentivit y period of the human eye) each point of the r eceivinglamp is illuminated for substantially only 7 one tinny-inwa ds Of second. It is obvious therefore that this pointby-point method of reproducing seriously curtails the degree of brilliancy in the integrated image and in some cases a blurring of the image results. This brilliancy, according to the invention, is

'materially increased and at the same time the image is reproduced as a visual whole by storing up the image impulses and reproducing the image as a unit under control of the said stored impulses. For this purpose eachof the electrodes I 3, M, I5, etc. has associated therewith a con-- denser I8, I9, 20, etc. These condensers are connected by a common conductor 2| with the interconnected strip electrodes H, I2, etc. The opposite terminals of the condensers I8, I9, 20 are connected by conductors 22, 23, 24, etc. to' corresponding fixed contacts 25, 26, 21, etc. in a rotating commutatoror distributor R. These latter terminals of the condensers C1 are also connected by conductors 28, 29,30, etc. to corresponding upper contacts in a multi-co-ntact switch SW1,

and thence through cooperating transfer contacts 3I, 32, 33, etc. to the corresponding electrodes I3, I4, I5 of the lamp I0. The above traced circuits between the condensers C1 and the electrodes I3, I4, I5, etc. are closed under control of the cam 34 which is adapted to be rotated from the same shaft 35 which carries the brush 36 of the commutator R. For this purpose the switch actuating lever'31 is provided with a cam follower 38 which cooperates with the raised and lowered portions of the cam 34. When follower 38 is on the raised face of the cam the above traced circuits are closed, and conversely when the follower 38 is on the lower face of the cam, the transfer contacts 3|, 32, 33, etc. are moved downwardly into engagement with the cooperating Sets of lower contacts. It is obvious therefore that when the contacts SI, 32, 33, etc. are closed on their upper contacts that discharge circuits are provided between each of the condensers in the bank 01 and the associated electrodes in the lamp I0 and a discharge is produced between each spaced electrode and the associated strip-electrode which discharge is proportional in intensity to the charge on the associated condenser.

For the purpose of short-circuiting the condensers C1 at the proper instant, the terminals thereof are connected to the contacts of a shortcircuiting switch SC1 which is operated by a cam 39 attached to the shaft 35. For the purpose of .storing the next complete image while the con- 40, 4!, 42, etc. to corresponding contacts in the switch SW1, which contacts are closed through the transfer contacts 3|, 32, 33, etc. thence to the corresponding electrodes I3, I4, I5, etc. when the cam follower 38 is on the lower face of the cam 34. A short-circuiting switch SCz similar to switch SC1 is provided for the purpose of shortcircuiting the condensers C2 at the proper instant,

switch SCz being operated by a similar cam 43.

Due to the duplicate arrangement of the condenser banks C1 and C2, each bank acts alternately as a storing means for a complete set of successive instantaneous image impulses and as tion shown in the drawing, it being understood that said brush is rotated at half the speed of the analyzing disc 4 under control of synchronizing means. As soon as brush 3.5 advances to the dotted line position the cam A3 momentarily operates switch SC2 and short-circuits all the condensers in the bank C2. After a fraction of an instant the switch 302 is released and the charging circuits for condensers C2 are closed. Im-

mediately thereafter brush 36 engages contact M which contact it will be understood closes synchronously with the scanning of a corresponding point of the image. Accordingly, the incoming image modulated impulse flows over conductor 46 to the right-hand terminal of condenser 47, the left-hand terminal of said condenser being connected through contact 44, brush 36, ring 50 tothe conductor 5! andthence to the other side of the transmission line, thus charging the condenser to a certain value. The succeeding image impulses are similarlyreceived and successively stored on the remaining condensers of the bank C2 until the entire image has been thus recorded in the form of charges on the individual condensers. After the last condenser has been charged corresponding to contact 52' the cam 39 operates switch SC1 and removes any -r esidual charge on the condensers C1, which have, during the preceding interval, been discharging through the lamp I0. At this instant also the follower. 38 rides on the lower face of cam 34 and closes discharge circuits between the condensers in bank C2 and the corresponding electrodes in the lamp I0. Thus the non-pictorial record of the image which was stored in the condensers C2 is simultaneously transferred through the contacts of switch SW1 to cause the selective illumination of the corresponding electrodes in the lamp l0 and with brilliances corresponding to the extent of charge 'on the respective condensers. For the purpose of maintaining this discharge image any suitable means such as the inductance or resistance elements ll may be connected in series with the discharge circuit. to increase the time constant of the discharge.

Accordingly, the entire image, due to the simultaneous discharge of the condensers C2 will remain on the lamp 13, while the brush 36 is contacting with the left-hand set of contacts of the switch R. During this latter half of the revolution of brush 36 the incoming image impulses are transmitted successivelyto the condensers C1 in a manner similar to that described in connection with condensers C2, this charging of condensers C1 being unaffected bythe discharge. of condensers C2 since the circuits for conductors 28, 29, 30, etc. are open at this time at the contacts of switch SW1, thus the next image is being stored on the condenser bank G1 at the same time that the bank C2 is discharging through the lamp H3. The foregoing sequence of operations is repeated for each revolution of brush 36, that is to say, one entire'image is being stored in a point-by-point fashion upon one condenser bank,

while the other condenser bank is simultaneously discharging an entire 'imagezthrough the lamp l0.

While in the foregoingdescription it has been chosen to embody the invention in specific apparatus, it will be understood that the invention is not confined thereto since its essence consists of the recording in a non-pictorial fashion of a complete record of an image at the same time that a preceding recorded image is being reproduced visually. While condensers have been shown for efiecting this storing it will be understood that equivalent mechanical devices might be employed with the same effect. Similarly, instead of using a single large reproducing lamp the same may be replaced by a plurality of individual lamps without departing from the spirit of the invention. It is also within the compass of the invention to employ other Well known visual reproducing means in place of glow discharge elements.

While it has been chosen to short-circuit the storing condensersby multi-contact switches it will be understood that in certain cases these switches may be optional, reliance being placed upon the condensers themselves to completely discharge through the lamp. Likewise, while elements 1'! havebeen shown for sustaining discharge by controlling the time constant of the discharge circuit these elements are optional. I In other words, the internal resistance of the lamp itself may be suificient to sustain the discharge for the desired length .of time. In any event, the capacities of the storing condensers is so chosen with respect to the remainingconstants of the discharge circuit that for 'a given applied voltage the discharge currents through the lamp produce the optimum optical force both as regards apparent brilliancy and permanency of impression. Other modifications will be apparent to those familiar with ,the'art of. television and it is contemplated that these modifications are within th scope of the invention.

What I claim is:

1. In a televisionsystem, meansfor translating picture points into corresponding electricalimpulses, means for receiving and non-visually storing said impulses in sequence to a plurality of luminous sources, and means for simultaneously releasing the stored impulses and thereby rendering all said sources effective in the reproduction of the image under control of said stored impulses.

2. In a television system, the method of increasing the brilliancy .of a reproduced image comprising non-visually storing in a sequential manner a complete image prior to its visual reproduction, and simultaneously releasing the stored energy for translating all elemental portions of said non-visual record simultaneously into a corresponding visual record.

3. The method of electrically transmitting images which comprises analyzing the image into a plurality of image. points, transmitting current impulses corresponding to the image point characteristics, and non-visuallystoring said impulses in sequence prior to visual reproduction and then subsequently releasing the complete series of stored impulses simultaneously to produce an electro-optical representation of a complete subject.

4. The method of transmitting and reproducing images electrically which comprises analyzing the image into corresponding image points, translating said points into,corresponding electric cur.- rent impulses, storing said impulses in sequence to produce a non-visual record of the image. and

then-translating said series of non-visual storage records simultaneously into a complete visual re production of the image.

5. Ina television system; the combination of means for translating an image into corresponding electric impulses, means for transmitting said impulses successively, means for non-visually storing in a sequential manner said successively transmitted impulses, and means effective upon the complete storing of said impulses for simultaneously releasing the stored impulses for reproducing the entireseries of image points therefrom so as to produce simultaneously a complete electro-optical image representation.

6. The method of electrically reproducing images which comprises producing sets of electrical impulses corresponding to the successive images, sequentially storing one'set of impulses and discharging all of the impulses of another set simultaneously and during the period when the first set of impulses is stored whereby each image is reproduced as a unit. I

7. In a television system means for producing sets of electrical impulses corresponding to successive images, means for non-visually storing one set of impulses and means for releasing as a unit during the time period of storage of one set'of impulses a previously stored set of impulses to reproduce the corresponding image as a unit.

8. In a television system means for translating the elements of an image into corresponding electric impulses and means for receiving and translating said impulses into an "electrostatic reproduction of the image produced sequentially for each point thereof, said last mentioned means comprising a plurality of banks of impulse storing devices, a variable light source and means for connecting each of the storage devices in said bank to said light source and simultaneously releasing all of the stored charges to energize the light sources.

9. In a television system means for producing current impulses corresponding to the elements of an image to be transmitted, a plurality of devices for storing said impulses, commutator means for successively energizing said storing devices under control of said impulses, an image reproducing device and commutator means for simultaneously connecting all of said storage devices to said image reproducing device.

10. In a television system means for receiving and reproducing an image at a distance comprising a plurality of sets of image impulse storing devices, an image reproducing device and means comprising a commutator and a plurality of switches for causing one of said sets of storing devices to store one image while another of said sets of storing devices is energizing said image reproducing means.

11. In a television system means for producing current impulses corresponding to image elements, a plurality of storing devices for storing said impulses, a commutator for selectively energizing said storing devices, an image reproducing device, a switch for connecting said selectively energized storing devices simultaneously to said reproducing device.

12. In a television system means for producing current impulses corresponding to image elements, a plurality of sets of devices for storing said impulses, an image reproducing device adapted to be energized under control of said storing devices, a multi-contact switch for alternately connecting .said storing devices to said reproducing device, and means-for causing an image tobe stored on one of said sets of devices while the other of saidsets is connected to said reproducing device.

13. Means for reproducing an image under control of electric-image impulses comprising a set of impulse storing devices, a commutator for controlling the selective energization of said storing devices, a switch actuated in response to the selective energization of said devices corresponding to a complete image, an image reproducing device adapted to be selectively energized in accordance with the energization of said storing devices when said switch is actuated and another switch for returning said storing devices to their normally deenergized condition in readiness for the reception of a set of impulses corresponding to a succeeding image.

14. The method of signalling, which comprises producing by scansiona series of electrical impulses representative of a subject, producing from the impulses a series of time displaced electrostatic charges, and releasing the stored charges simultaneously at a time period subsequent to the time when charges representing a complete subject are produced.

15. In a signalling system, means for producing a series of time displaced impulses corresponding to the message to be transmitted, means for storing said impulses in sequence, means for retransmitting the said impulses simultaneously at a time period subsequent to the sequential storage of a series of impulses corresponding to the message, and meansfor receiving the simultaneously retransmitted impulses to reproduce as a unit the original message from which the charges were initiated.

16. In receiving apparatus employed in the art herein described, the combination of a picture plane, means embodying a gaseous lamp for transiently exciting illumination of said picture plane in elementary areas, means for sequentially storing a series of electro-static charges representing each elemental area of the picture to be electro-optically reproduced, means for simultaneously releasing all of said stored charges subsequent to said storage, and means including a condenser and a resistance in circuit with the gaseous lamp for securing persistence of illumination of said elementary areas subsequent to the release of said charges for a time approximately equal to persistence of vision of the human eye.

17. In a television system, means for increasing the brilliancy of a reproduced image comprising means for electrically storing in a sequential manner a complete image prior to its visual reproduction, subsequent to the period of storage releasing the complete series of stored charges simultaneously, and producing light values over each elemental area of a viewing plane in accordance with the simultaneously released charges.

I 18. In an electroeoptical image producing system, means for scanning the elemental areas of afield of view cyclically in succession to produce an image current, an' image producing device comprising a plurality of groups of elements, and means for actuating the elements of one group only during one scanning period and another group in the same general order during a succeeding scanning period.

EDWARD D. PHINNEY. 

